Overview

Carotid artery dissection is a tear in the intima of the carotid artery wall causing separation of the wall layers. The carotid artery supplies blood to the head and brain. Carotid dissection is an important cause of stroke in young adults.

Pathophysiology

Arterial dissection of the carotid arteries occurs when a small tear in the innermost lining of the arterial wall forms. Blood can enter into the space between the inner and outer layers of the vessel, creating an intraluminal hematoma which forms a thrombus causing narrowing (stenosis) or complete occlusion. This thrombus can act as a nidus for distal embolization to the brain. Extracranial dissection of internal carotid artery is more frequent than intracranial dissection. The stenosis that occurs in the early stages of arterial dissection is a dynamic process and some occlusions can return to stenosis very quickly[1]. When complete occlusion occurs, it may lead to ischemia. Often, even a complete occlusion is totally asymptomatic because collateral circulation in the head keeps the brain well perfused. However, when blood clots form and break off from the site of the tear, the clots travel through the blood to the brain and clog one or more of the arteries directly supplying the brain, resulting in an ischemic stroke, otherwise known as an infarct. Blood clots, or emboli, originating from the dissection are thought to be the cause of infarction in the majority of cases of stroke in the presence of carotid artery dissection. Cerebral infarction causes irreversible damage to the brain. In one study of patients with carotid artery dissection, 60% had infarcts documented on neuroimaging[2][1] .

Causes

The cause of internal carotid artery dissection can be broadly categorized into two classes: spontaneous or traumatic.

Spontaneous

Once considered uncommon, spontaneous carotid artery dissection is an increasingly recognized cause of stroke that preferentially affects the middle-aged[3].

Nevertheless, although an association exists with connective tissue disorders does exist, most people with spontaneous arterial dissections do not have associated connective tissue disorders.

Traumatic

Carotid artery dissection is more commonly thought to be caused by trauma to the head and/or neck. The probable mechanism of injury for most internal carotid injuries is rapid deceleration, with resultant hyperextension and rotation of the neck, which stretches the internal carotid artery over the upper cervical vertebrae, producing an intimal tear[4]. After such an injury, the patient may remain asymptomatic, have a hemispheric transient ischemic event, or suffer a stroke[5].

Differentiating Carotid Artery Dissection from other Diseases

Carotid artery dissection should be differentiated form the following:

Epidemiology and Demographics

The annual incidence of spontaneous carotid artery dissection is low, and incidence rates for internal carotid artery dissection have been reported to be 2.6 to 2.9 per 100,000[6].

Prevalence of hereditary connective tissue diseases in people with spontaneous dissections is highly variable, ranging from 0% to 0.6% in one study to 5% to 18% in another study.

An estimated 0.67% of patients admitted to the hospital after motor vehicle accidents were found to have blunt carotid injury, including intimal dissections, pseudoaneurysms, thromboses, or fistulas[7]. Of these, 76% had intimal dissections, pseudoaneurysms, or a combination of the two.

Gender is not associated with an increased risk of carotid artery dissection.

Complications and Prognosis

Complication

Prognosis

Prognosis of carotid artery dissection is favorable with 75% of patients having a good recovery. Traumatic dissection is associated with a higher mortality rate on discharge compared to spontaneous dissection. Two important prognostic factors include: